All my friends and I rode our bikes to school (see my avitar for the bike I rode) and never locked them. The school was located in suburban NJ. In 6 years of doing this only ONE bike was ever stolen. It was an English 10 speed and for that reason was probably stolen by pros.
In the same area, about a year ago, I had some idiot steal the 2 batteries out of my $ store scan radio at my local library. The radio was thrown to the ground but the cretin stole 2 , 8- for-a-buck batteries that were almost dead! The irony is that the library is about 35 yards from the police station and the duty officer can see the bike area from his window. So someone with about 25 brain cells stole 25 cents worth of dead batteries right in front of the cops.! No point to the story, except that public behavior has deteriorated so dramatically in a half century.
I used to think that this decline was due to the prevalence of child-proof caps. You know any kid stoopid enough to drink the contents of a container from under the kitchen sink w/o smelling/tasting same deserved to not pass on his genes. Then I discovered that a US govt. survey found that due to the use of childproof caps and parents child-proofing cabinents, parents no longer try to instill any caution in their spawn, and the death rate from "accidental" poisoning is almost EXACTLY THE SAME as it was b4 this.: I must now return to my previously schedualed shouting at kids to stay off the lawn!